Intermixing syringe

ABSTRACT

An intermixing syringe provides for the isolated storage of two components prior to their being mixed which is usually just before injection of the product. This syringe has an outer barrel and a hollow plunger slidable therein with the barrel portion forward of the piston providing one chamber of determined size and the plunger provides the other chamber. The plunger is provided with and carries on its forward end a piston having spaced, ring-like sealing surfaces. The plunger is a closed hollow cylinder having apertures at its forward end and in its outer wall near its rear end. Tear members are attached to the plunger at these apertures to seal and make these apertures fluid tight. In the piston is formed a fluid passageway extending from the interior of the piston to the outer piston surface. The barrel has a smooth straight-bored inner surface and is absent any undercuts.

United States Patent [1 1 3,678,930 Schwartz 1 July 25, 1972 INTERMIXING SYRINGE FOREIGN PATENTS OR APPLICATIONS 72 Inventor: B i Schwartz, 00 p Ave" Paterson, l,49l,785 l0/l969 Germany ..128/218 M Primary Examiner-Richard A. Gaudet [22] Filed! J 1971 AssislamExaminerJ. C. McGowan Appl. No.: 107,645

Attorney-Ralph R. Roberts [57] ABSTRACT An intermixing syringe provides for the isolated storage of two components prior to their being mixed which is usually just before injection of the product. This syringe has an outer barrel and a hollow plunger slidable therein with the barrel portion forward of the piston providing one chamber of determined size and the plunger provides the other chamber. The plunger is provided with and carries on its forward end a piston having spaced, ring-like sealing surfaces. The plunger is a closed hollow cylinder having apertures at its forward end and in its outer wall near its rear end. Tear members are attached to the plunger at these apertures to seal and make these apertures fluid tight. In the piston is formed a fluid passageway extending from the interior of the piston to the outer piston surface. The barrel has a smooth straight-bored inner surface and is absent any undercuts.

11 Claims, 6 Drawing Figures Patentod July 25,1972 7 3,678,930

Fig 4 INVENTOR BORIS SCHWARTZ AGENT INTERMIXING SYRINGE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the general class of Surgery", and more particularly to the subclass of syringes".

2. Description of the Prior Art Syringes are well known in the general field of surgery and those for storing and intermixing various ingredients are represented in patents as to PIERICK, US. Pat. No. 3,279,654 of Oct., 1966; to BROWN, US Pat. No. 2,591,046 of Apr., I952; and to CAMBER, Great Britain Pat. No. 746,057 of Jan. 1959. These and other patents are gravity to induce a flow of one component from one chamber to another. Many require an exact manipulation of the syringe by the user who may not have the required skill or training. The precise and exact mixing of the various components comprising some of the new medicants is an absolute necessity. Ease of mixing by a potential administrator of the medicant is necessary and desirable, and such a manipulative device is an object of this invention. The providing of positive isolation of the stored fluid is a great problem of the storage of many of these components.

In my US Pat. No. 3,464,412 which issued on Sept. 2nd, 1969, I used the principle of reduced pressure to draw the fluid from the follow plunger to and through a fluid passageway in the side of the piston and then through an undercut or relief formed in the bore of the barrel. The forward sealing rings of the piston were rendered ineffective as sealing means as they were brought in way of the undercut portion or portions in the barrel and the fluid flowed past these rings to the forward compartment in the barrel. In the present invention, undercuts are not provided; however, the forward sealing means is rendered selectively inefiective by designing the piston so that a determined level of reduced pressure, when developed in the forward portion of the barrel, causes the forward sealing means of the piston to be displaced inwardly sufficiently to permit fluid from the plunger to flow past the piston sealing means.

The syringe of the present invention provides a means for bringing the forward portion of the barrel of the syringe into a condition of reduced pressure. At a predetermined level of reduced pressure, a flow conducting portion of the piston of a hollow plunger is brought into a fluid passing condition so that fluid flows from the plunger. This fluid which is stored in the plunger is sucked from the plunger interior to flow past the piston into the forward housing chamber to provide a controlled mixing of the stored ingredients.

The plunger of the present invention in its initially stored condition is provided as a closed hollow cylinder having a reduced and contoured forward end disposed to receive and retain thereon a slidable piston movable to determined limits on the plunger. An aperture formed in this forward end of the plunger is sealed by a tear-away member attached to the plunger at and around this aperture. The tear-away member is actuated to uncover the aperture by the rearward movement of the plunger in the outer housing or barrel. Another or second aperture is formed in the sidewall of the plunger barrel preferably at a point near its rear or outer end. Another or second tear-away member is fastened to the plunger sidewall at this second aperture to seal this aperture until the time the plunger is drawn outwardly in the barrel of the syringe. This same outward movement of the plunger which actuates the forward tear-away member to uncover the first aperture also actuates the rear tear-away member to uncover the rear or second aperture.

SUMMARY OF THE INVENTION This invention provides a syringe-type apparatus having an outer housing or barrel of generally tubular construction which is formed with an open rear end and a restricted forward end. This forward end has an aperture or passageway through which the mixed medicant or fluid and the like is expelled from the syringe, usually to and through a needle. The initially assembled plunger is a closedhollow cylinder slidable in the bore of the barrel and in its hollow interior is stored the fluid component. Its forward end has a neck portion upon which is mounted a slidable piston having a fluid-flow passageway extending from the outer surface of the piston to the interior of the piston. The inner surface of the barrel portion of the outer housing is a straight bore in which the piston is slidable. The forward end of the piston is provided with at least one sealing ring disposedto permit forward fluid flow from the interior of the piston to the outer housing or barrel, but no rearward or reverse fluid flow. The hollow plunger has a first aperture formed in its forward neck portion, said aperture providing a flow passageway from the interior of the plunger to the interior of the piston. This aperture is sealed by a tear-away member which is contemplated to be actuated to uncover the sealed aperture by a rearward movement of the plunger. A second aperture is formed in the sidewall of the plunger barrel at a point near its rear end. This second aperture is sealed by a second tear-away member which is contemplated to be actuated to uncover the sealed aperture by a rearward movement of the plunger. 7

In the embodiment of this invention the syringe is arranged primary as an intermixing syringe with one ingredient stored in the foreportion of the housing or outer barrel and another ingredient which is fluid is stored in the hollow plunger member of the syringe. It is an object of this invention to provide an intermixing syringe assembly in which two medicants may be isolated for storage and which at a determined time and by manipulative action are mixed usually immediately prior to the use of the medicant. The intermixing of the components is accomplished when the plunger is manipulated to move the plunger and piston outwardly from a forward position so that the forward portion of the barrel is brought into a condition of reduced pressure. As the plunger is pulled rearwardly in the housing tear-away members at the front and rear of the plunger are actuated to uncover previously sealed apertures to permit fluidflow to be sucked from its stored condition in the barrel to the reduced pressure forward portion of the oute barrel whereat the components are mixed.

It is a further object of this invention to provide an intermixing syringe wherein two components of the medicant are positively isolated for storage until the time of mixing. Positive hermetic isolation of the fluid component is provided by a sealed hollow tubular plunger having tear-away members removably attached to the sealed front and rear apertures formed in the walls of the plunger.

INTENT OF THE DISCLOSURE Although the following disclosure ofi'ered for public dissemination is detailed to insure adequacy and aid in understanding of the invention, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how it may later be disguised by variations in form or additions of further improvements. The claims at the end hereof are intended as the chief aid toward this purpose, as it is these that meet the requirement of pointing out the parts, improvements or combinations or methods in which the inventive concepts are found.

There has been chosen a specific embodiment of an intermixing syringe adapted for positive fluid isolation during storage and showing a preferred means for actuating tearaway sealing members by actuation of the plunger. This specific embodiment has been chosen for the purposes of illustration and description as shown in the accompanying drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 represents a sectional view of the intermixing syringe of this invention with the plunger in the forward stored position;

FIG. 2 represents an enlarged sectional view of the forward end of the plunger with the sealing member shown in a disconnected position;

FIG. 3 represents an end view of the end of the plunger of FIG. 2 with the sealing member in attached condition, the view taken on the line 3-3 of FIG. 2;

FIG. 4 represents an enlarged sectional view of the rear end of the intermixing syringe and showing the plunger with its rear scaling in a disconnected condition;

FIG. 5 represents a side view of a porous bag container for powder medicants and the like, and

FIG. 6 represents an enlarged sectional view of the forward end of the assembled plunger.

In the following description and in the claims various details will be identified by specific names for convenience; these names, however, are intended to be generic in their application. Corresponding reference characters refer to like members throughout the several figures of the drawing.

The drawing accompanying, and forming part of, this specification discloses certain details of construction for the purpose of explanation of the broader aspects of the invention, but it should be understood that structural details may be modified in various respects without departure from the concept and principles of the invention and that the invention may be incorporated in other structural forms than shown.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the syringe as seen in FIG. I through 6 it is to be noted that an outer barrel 10 may be made of glass, plastic or other material and is formed with a reduced forward end with a reduced bore 11 and taper 12 adapted to receive the hub of a needle. This small bore is conventional for the passage of fluid, medicants or the like. The rear portion of the barrel 10 preferably has a flange 14 of conventional elliptical construction providing means for the ready grasping of the syringe by the operator. The bore 16 of the barrel is assumed to be both regular and circular in configuration within reasonable manufacturing tolerances and without undercuts and the like extends from the front end to the rear end of the barrel with a substantially like diameter. On the rear flange 14 of the housing there is contemplated to be mounted a shield 20 which is preferably a snap-on plastic or rubber member. In this shield is formed a determined bore 22 in which is slidable a plunger 24 to be more fully hereinafter described. The outer diameter or surface 26 of this plunger 24 is made of a like diameter except at its rear end which is provided with a closing end disc 28 of an enlarged diameter.

The forward portion of the plunger 24 is better seen in enlarged detail in FIGS. 2, 3 and 6 wherein the front end has a reduced diameter 30 providing an elongated sliding surface of determined diameter terminating in a forward stop flange 32 also of a determined larger diameter. A portion of this enlarged forward stop flange 32 is cut away at 34 to provide a slot for the. passage therethrough and guiding retention of a tongue end 36 of a tear-away seal member 38 which may be of plastic or the like. This tear-away seal member, as shown, is formed in the shape, of an L" with an upper inwardly extending tab portion 40 and a sealing member portion 42.extending inwardly of main bar portion 44 which is the vertically disposed portion of seal member 38 as seen in FIG. 2. The tab portion 40 is sized and shaped so as to be engaged and retained in a socket 48 formed in the forward face of the flange 32 of the plunger 24. The extending tab 42 is disposed in way of a discharge aperture 50 formed in end wall 52 of the plunger 24. The tab 42 is sealed or mounted in aperture 50 so as to provide a fluid-tight condition when in the stored condition of FIGS. I and 6. In its assembled condition as seen in FIGS. 1 and 6 the tongue end 36 extends rearwardly of the flange 32 and lays adjacent reduced diameter 30 of the barrel with tab 40 pivotally resting or seated in the socket 48 of the plunger. Sealing member 42 is firmly mounted in way of aperture 50 to provide a fluid-tight seal either as a plug or by fusion over the aperture.

Referring particularly to FIGS. I and 4 it is to be noted that in its assembled state the rear portion of the plunger 24 has a lever arm 60 attached to its outer diameter. This arm has an inwardly extending end 62 attached to the barrel by welding and the like so that the inner end provides a fluid-tight seal of a rear aperture 64 formed in the side of the barrel. The forward end of this arm 60 is formed with a latch end 66 and in its stored condition this latch is disposed to engage the forward face of the shield 20 during the rearward movement of the plunger 24 and the attached lever portion 60.

Mounted on the reduced shank 30 of the forward end of the plunger 24 as seen in FIGS. 1 and 6 is a piston 70 which has a rear engaging flange portion 72 disposed to slide upon the outer diameter surface 30 of the plunger. Forward of flange 72 is an enlarged diameter portion 73 providing a relief of a determined length. On the piston 70 there is provided a forward end 74 which extends outwardly to form a ring 78 best seen in FIG. 6. The rear flange portion 72 is slidable on surface 30 and the enlarged diameter 73 is slidable on flange 32. The forward end 74 has its inner end contoured at 76 to received tear-away seal member 38. The ring-like lip 78 is sloped forwardly to provide a fluid-tight seal for the plunger as the plunger is moved forwardly and to partially collapse to permit fluid bypass when the plunger is drawn rearwardly. At least one fluid passageway 80 is formed in the sidewall of the piston 70.

use AND OPERATION The outer barrel 10 of the intermixing syringe of this invention is of the conventional configuration found in standard syringes. When used as a storage chamber the forward passageway 11 of the tapered end 12 is provided with a plug as seen in phantom outline in FIG. I. This plug is usually of rubber or plastic and when mounted prevents the outflow of any powder or the like stored within the barrel 10. This plug also provides a stop to any'flow of air from the outside into the forward portion of the barrel 10. The plunger 24 has its front end made as seen in FIG. 2 and prior to filling the plunger tear-away seal member 38 is mounted to close aperture 50. This is accomplished by either a friction plug seal or by a seal such as a heat seal causing aperture 50 to be sealed so as to prevent any fluid flow through aperture 50 until the seal member 42 is pulled from in way of the aperture. Through the rear aperture 64 a determined quantity of fluid may be fed into the interior of the plunger 24 after which arm 60, which may be plastic or glass, is caused to be sealed to the outer surface of plunger 24 to provide a positive seal to the passage of air or to a leaking of fluid from the barrel.

As thus sealed the fluid in the barrel is positively retained until there is a manipulation of the syringe. In the foreportion of the barrel I0 there may be stored a powder or other form of medicants. The piston 70 is caused to be mounted on the front end the plunger so that the bore 16 of the barrel is sealed in the customary manner. It is contemplated that in its assembled and stored condition the piston 70 is at its rear position as in FIG. 6 and flange 72 is adjacent the rear shoulder of reduced 30 where it joins the enlarged barrel portion of the plunger. Tear-away seal member 38 is seated in the forward portion in piston 70 which is forwardly in barrel 10 to provide a storage condition.

When the syringe is to be usedv and the stored ingredients are to be mixed it is contemplated that the barrel will be grasped at least partially by flange l4. Plunger 24 is grasped at flange or disc 28 and pulled rearwardly so that arm 60 as it engages the shield 20 is caused to be torn from its attachment to the barrel to cause the end 62 to the dislodged or torn free as seen in FIG. 4 and to uncover rear aperture 64. This permits any stored fluid within the plunger 24 to freely flow therefrom when the other opening 50 is uncovered. This does not occur however, until the piston 70 has been drawn rearwardly in bore 16 and is brought into engagement with shield 20, whereupon the flange portion 72 of the piston engages the shield. The piston is then stopped in its movement as this shield engages the rear end of arm 36. As the plunger is continued to be pulled rearwardly the arm 36, in the manner of a lever, is moved with tab 40 pivoting in socket 48 and causing the end 42 to be dislodged or broken from sealing engagement of aperture 50 to uncover this aperture.

The rearward movement of the plunger 24 causes the forward area of the barrel to be brought into a condition of greatly reduced pressure. When the aperture 50 is uncovered the fluid in the plunger 24 is drawn by the reduced pressure through aperture 50, aperture 80 and forwardly around the sealing ring 78 which, as constructed, provides a one-way flow valve in that the ring is deflected forwardly to permit a flow of fluid thereby. As the fluid is transferred to the forward portion of the outer barrel the flow is rapid and vigorous providing a desired mixing of the stored powder and fluid. This flow action usually completes the intermixing required, or if not, a small shake by the administrator of the syringe enables the mixing to be completed. At this point the plunger is at its rearward stroke. The syringe is now turned so the small end is in an upward position whereat the sealing plug 90 is removed from the opening 11 and a conventional hub needle is mounted thereon. The piston 70 is then caused to be pushed forward until any residual air in the syringe is expelled from the barrel and needle, after which the syringe is used in the customary manner for administration to the patient.

It is to be noted that as the plunger 24 is drawn rearwardly from the stored position of FIG. 1 the lever arm 60 is deflected so as to break from the barrel of the plunger. As it, the arm, becomes separated it may be discarded or allowed to fall to the floor for discarding at a more convenient time. At the rearmost position of the plunger, whereat the tear-away seal member 38 is pulled from its attached condition of FIG. 6, the member 38 falls within the recess 73 and lays in this cavity as the plunger is moved forwardly. The tongue end 36 remains in slot 34 so that main bar 44 is the only portion of the member 38 which may lay against end 74 as piston 70 is moved forwardly. Usually flange portion 72 provides essentially all the required support for the piston in its forward thrust. It is also customary for plug 90 to be discarded at the time the needle is mounted on taper 12. Of course the plunger 24, sealed at apertures 50 and 64, once opened by manipulating the tearaway seals is very difficult to reuse, hence the whole syringe becomes a throw-away product.

DESCRIPTION OF THE BAG OF FIG. 5

In certain instances the powder to be stored in the barrel may be difficult to feed into the foreportion of the barrel in a loose condition. When this occurs, a bag member made out of a porous fiber, porous glass or the like, may be utilized to receive a determined quantity of powder, whereupon the open end of the bag is closed by sealing, stitching or the like, so that the bag is in the form of a tubular sealed pouch 100 as seen in FIG. 5. The powder thus packaged, may be slid into the barrel 10 for storing therein while the plunger with the piston 70 at tached thereto is slid into the barrel while the passageway 11 is left in an open condition, This permits any air in the barrel 10 to be expelled and a plug 90 to be installed in the passageway l 1. Means other than inserting a plug 90 may be used such as mounting a sealing cap on the taper 12. Any seal which will isolate and maintain the sterility of the contents of the syringe until time for us may be used. The sealed cap,not shown, when mounted upon the tapered hub 12 is left in place until after the intermixing has been completed, at which time the cap is removed and the hub of the needle is mounted on the taper with the syringe used in the usual manner. The fluid when it flows to and around the bag I00 is mixed with the powder in the bag and when mixing is complete the plunger 24 is moved forwardly with bag 100 being pushed into a minimum volume and the mixture being expelled through the needle. The bag 100 acts to a certain extent to provide a filtering means. This plunger also provides a simple means for ascertaining whether the syringe has been tampered with prior to use since manipulation of the plunger will certainly cause pull-away lever arm 60 to be dislodged indicating tampering.

It is also to be noted that the rear aperture 64 may be covered by a pressure sensitive tape wherein a selected flexible plastic strip has one face at least locally coated with an ad hesive so that when pressed over the aperture 64 the aperture is sealed. At the time of use the operator may grasp a free portion and strip the tab from the plunger thereby uncovering the aperture. If desired when the aperture 64 is to be covered by a tape the aperture may be formed in the rear end wall of the plunger.

Terms as left", right, up", down, bottom", top", front", back", in, "out" and the like are applicable to the embodiment shown and described in conjunction with the drawing. These terms are merely for the purposes of description and do not necessarily apply to the position in which the intermixing syringe may be constructed or used.

The conception of the sealed hollow plunger and its many applications is not limited to the specific embodiment shown but departures therefrom may be made within the scope of the accompanying claims and protection is sought to the broadest extent the prior art allows.

What is claimed is:

1. An intermixing syringe for the isolated storage of at least two medicant portions and the like, the syringe including an outer housing having an open rear end and a partially closed front end with a passageway therethrough, and a hollow plunger carrying on its front end a piston slidable in the bore of the housing and in its hollow portion providing for the isolated storage of at least one of the stored medicant portions, the syringe including means whereby at least one of the medicant portions may be transferred from the hollow plunger to the housing for the mixing of the portions, the syringe having means for bringing the stored portion in the housing and the same housing portion into a condition of reduced pressure, the syringe comprising (a) an outer housing of generally tubular configuration having an inner bore of a generally constant cross-section, the housing having a front partially-closed end with a discharge passageway therethrough; (b) removable means for selectively closing the passageway of the partiallyclosed front end of the housing so as to prevent the passage therethrough of air, fluids and the like; (c) a hollow plunger of a closed construction and having a main portion of generally tubular configuration sized to easily move axially in the bore of said outer housing without sealing of the bore of the housing; (d) a front end of the plunger in which there is provided a reduced diameter portion of determined length terminating in a forward flange of a determined larger diameter; (e) an end wall provided at the forward end of the plunger said wall having a front aperture therethrough for the flow of fluid; (f) a tear-away seal member carried by the plunger and disposed to seal the aperture in the forward end wall of the plunger; (g) a resilient piston mounted and sliding on the reduced diameter portion of the forward end of the plunger, said piston having at least one forward ring-like sealing surface sized so as to be slidable in the bore of the housing while engaging said bore in a fluid'flow sealing manner, the piston having at least one flow passageway formed in its side wall with one end of the passageway open to the interior of the plunger and the other end terminating at the piston outer surface and rearwardly of a forward ring-like sealing surface, said piston further formed so that those ring-like sealing surfaces forward of the formed flow passageway are deflectable from a sealing condition to a fluid-flow forwardly condition permitting the fluid in the plunger to flow through said passageway and past the forward sealing surfaces and into the forward housing portion when said forward housing portion is brought to a condition of reduced pressure, said piston further having at least one ringlike sealing surface rearwardly of the flow passageway through the sidewall of the piston; (h) means on said outer housing engaging said piston upon rearward movement of the plunger in the housing whereby said piston actuates and tear-away seal member to uncover said forward aperture; (i) a rear aperture formed in the plunger near its rear end, and (j) a sealing means providing a tear-away seal adapted to close said rear aperture to provide a fluid-tight closure, said sealing means being readily removed from the aperture to uncover the aperture by manipulation of the syringe by the user.

2. An intermixing syringe as in claim 1 in which the engaging means is a flange on the rear end of theouter housing and upon which is mounted a shield having a bore sized to slidably retain the outer diameter of the plunger and to provide a stop shoulder to the rearward movement of the resilient piston slidably carried on the the reduced diameter front end of the plunger.

3. An intermixing syringe as in claim 2 in which the flanged front end of the plunger is formed with a cut away portion providing a slot, and in which the forward tear-away seal member is generally L"-shaped with the leg portion slidable in the slot in the flanged end and in its sealed condition said leg portion extends rearwardly of the flanged front end in which a main bar portion of the L-shaped member has a tongue end adapted to seat and pivot in a socket in the plunger with a sealing portion on the main bar adapted to be brought in way of the front aperture and to be mounted on the end of the plunger to seal the forward aperture.

4. An intermixing syringe as in claim 3 in which the sealing of the aperture is by welding the sealing portion of the main bar to the end of the plunger.

5. An intermixing syringe as in claim 3 in which the sealing of the aperture is by cementing the sealing portion of the main bar to the end of the plunger.

6. An intermixing syringe as in claim 3 in which the sealing of the aperture is by a plug portion on the main bar shaped and sized so as to provide a fluid-tight closure when it is press-fit mounted in the aperture.

7. An intermixing syringe as in claim 3 in which the piston is formed with a rear inwardly-extending flange portion disposed to slide on the outer reduced diameter surface of the plunger, and in which adjacent said inwardly extending flange then is provided with an enlarged portion sized to slide by the slot retained leg portion of the "-shaped tear-away member while permitting the inwardly-extending flange portion of the piston to be moved in way of and then engage the leg portion of the tear-away member to move the tear-away member into an aperture uncovering condition.

8. An intermixing syringe as in claim 1 in which the sealing means for the rear aperture is a lever am having means for releasably engaging the outer housing so that said lever arm is actuated during and by the withdrawal movement of the plunger in the housing, said actuation causing at least a partial uncovering of the rear aperture in the plunger.

9. An intermixing syringe as in claim 8 in which the lever arm is attached to the barrel of the plunger by welding and in which the releasable engagement of the outer housing is a latch portion on the lever arm adapted to engage the forward face of the flange-mounted shield.

10.. An intermixing syringe as in claim 8 in which the lever arm is attached to the barrel of the plunger by cementing and in which the releasable engagement of the outer housing is a latch portion on the lever arm adapted to engage the forward face of the flange-mounted shield.

11. An intermixing syringe as in claim I in which sealing of the rear aperture in the plunger is by an adhesive strip which may be removed from the aperture by manipulative pulling by the operator at the time of preparing the syringe for use. 

1. An intermixing syringe for the isolated storage of at least two medicant portions and the like, the syringe including an outer housing having an open rear end and a partially closed front end with a passageway therethrough, and a hollow plunger carrying on its front end a piston slidable in the bore of the housing and in its hollow portion providing for the isolated storage of at least one of the stored medicant portiOns, the syringe including means whereby at least one of the medicant portions may be transferred from the hollow plunger to the housing for the mixing of the portions, the syringe having means for bringing the stored portion in the housing and the same housing portion into a condition of reduced pressure, the syringe comprising (a) an outer housing of generally tubular configuration having an inner bore of a generally constant crosssection, the housing having a front partially-closed end with a discharge passageway therethrough; (b) removable means for selectively closing the passageway of the partially-closed front end of the housing so as to prevent the passage therethrough of air, fluids and the like; (c) a hollow plunger of a closed construction and having a main portion of generally tubular configuration sized to easily move axially in the bore of said outer housing without sealing of the bore of the housing; (d) a front end of the plunger in which there is provided a reduced diameter portion of determined length terminating in a forward flange of a determined larger diameter; (e) an end wall provided at the forward end of the plunger said wall having a front aperture therethrough for the flow of fluid; (f) a tear-away seal member carried by the plunger and disposed to seal the aperture in the forward end wall of the plunger; (g) a resilient piston mounted and sliding on the reduced diameter portion of the forward end of the plunger, said piston having at least one forward ring-like sealing surface sized so as to be slidable in the bore of the housing while engaging said bore in a fluid-flow sealing manner, the piston having at least one flow passageway formed in its side wall with one end of the passageway open to the interior of the plunger and the other end terminating at the piston outer surface and rearwardly of a forward ring-like sealing surface, said piston further formed so that those ringlike sealing surfaces forward of the formed flow passageway are deflectable from a sealing condition to a fluid-flow forwardly condition permitting the fluid in the plunger to flow through said passageway and past the forward sealing surfaces and into the forward housing portion when said forward housing portion is brought to a condition of reduced pressure, said piston further having at least one ring-like sealing surface rearwardly of the flow passageway through the sidewall of the piston; (h) means on said outer housing engaging said piston upon rearward movement of the plunger in the housing whereby said piston actuates and tearaway seal member to uncover said forward aperture; (i) a rear aperture formed in the plunger near its rear end, and (j) a sealing means providing a tear-away seal adapted to close said rear aperture to provide a fluid-tight closure, said sealing means being readily removed from the aperture to uncover the aperture by manipulation of the syringe by the user.
 2. An intermixing syringe as in claim 1 in which the engaging means is a flange on the rear end of the outer housing and upon which is mounted a shield having a bore sized to slidably retain the outer diameter of the plunger and to provide a stop shoulder to the rearward movement of the resilient piston slidably carried on the the reduced diameter front end of the plunger.
 3. An intermixing syringe as in claim 2 in which the flanged front end of the plunger is formed with a cut away portion providing a slot, and in which the forward tear-away seal member is generally ''''L''''-shaped with the leg portion slidable in the slot in the flanged end and in its sealed condition said leg portion extends rearwardly of the flanged front end in which a main bar portion of the ''''L''''-shaped member has a tongue end adapted to seat and pivot in a socket in the plunger with a sealing portion on the main bar adapted to be brought in way of the front aperture and to be mounted on the end of the plunger to seal the forward aperture.
 4. An intermixing syringe as in claim 3 in which the sealing of the aPerture is by welding the sealing portion of the main bar to the end of the plunger.
 5. An intermixing syringe as in claim 3 in which the sealing of the aperture is by cementing the sealing portion of the main bar to the end of the plunger.
 6. An intermixing syringe as in claim 3 in which the sealing of the aperture is by a plug portion on the main bar shaped and sized so as to provide a fluid-tight closure when it is press-fit mounted in the aperture.
 7. An intermixing syringe as in claim 3 in which the piston is formed with a rear inwardly-extending flange portion disposed to slide on the outer reduced diameter surface of the plunger, and in which adjacent said inwardly extending flange then is provided with an enlarged portion sized to slide by the slot retained leg portion of the ''''L''''-shaped tear-away member while permitting the inwardly-extending flange portion of the piston to be moved in way of and then engage the leg portion of the tear-away member to move the tear-away member into an aperture uncovering condition.
 8. An intermixing syringe as in claim 1 in which the sealing means for the rear aperture is a lever arm having means for releasably engaging the outer housing so that said lever arm is actuated during and by the withdrawal movement of the plunger in the housing, said actuation causing at least a partial uncovering of the rear aperture in the plunger.
 9. An intermixing syringe as in claim 8 in which the lever arm is attached to the barrel of the plunger by welding and in which the releasable engagement of the outer housing is a latch portion on the lever arm adapted to engage the forward face of the flange-mounted shield.
 10. An intermixing syringe as in claim 8 in which the lever arm is attached to the barrel of the plunger by cementing and in which the releasable engagement of the outer housing is a latch portion on the lever arm adapted to engage the forward face of the flange-mounted shield.
 11. An intermixing syringe as in claim 1 in which sealing of the rear aperture in the plunger is by an adhesive strip which may be removed from the aperture by manipulative pulling by the operator at the time of preparing the syringe for use. 